The present invention relates generally to secure digital input output (SDIO), and more particularly, to a mechanism for placing an SDIO device in a sleep mode and waking up the SDIO device from the sleep mode.
Secure digital input output (SDIO) is an interface standard extended from secure digital (SD) standard, which not only can be applied in storage devices like flash memory cards, but also can be used to interface peripheral devices such as Wi-Fi wireless network cards, global positioning system (GPS) receivers, and Bluetooth adapters. Typically, an SDIO card that is combined with the above-mentioned Wi-Fi network card, GPS receivers, and Bluetooth adapter is called an SDIO device. The SDIO device is hosted by an SDIO host, together forming an SDIO system. Sometimes, functions on the SDIO device provided by the peripheral devices may be temporarily unnecessary for the user. In order to reduce the power consumption of the SDIO system, the SDIO device may be switched to an idle mode by using clock gating technique. Such technique can effectively reduce the dynamic power dissipation by disabling the switching of logic gates in the SDIO device. However, the static power dissipation caused by the leakage current cannot be reduced by the clock gating technique.
A common method of reducing the static power dissipation is to reduce a level of a supply voltage supplied to the SDIO device. However, in some conditions, if the level of the supply voltage is decreased to a certain extent, the capability of the SDIO device for receiving incoming signals sent from the SDIO host may be affected. This is because it is hard for a receiver of the SDIO device to correctly decode the high frequency signals defined in the SDIO specification, while being operated with low supply voltage. In the worst case, the SDIO device may fail to receive the signal that is used for waking up the SDIO device from the idle mode. This disadvantageously increases the time required by waking up SDIO device and correctly responding to the SDIO host.
It is thus desirable to have a mechanism that is capable of waking up SDIO device that is supplied with a lower supply voltage.